Diseased blood vessels are a widespread medical condition. For example, atherosclerotic plaque may develop in blood vessel walls, a thrombus (blood clot) may form in a vessel, or a stenosis may form. If a blood vessel becomes weakened, or if the accumulation of plaque or thrombi on blood vessel walls becomes too severe, surgical intervention may be required to prevent rupture or complete occlusion of the vessels. While many different surgical procedures are associated with alleviating this condition, the use of catheters is preferred, due to the minimally invasive nature of procedures involving catheters.
Many types of procedures involve the use of catheters to treat stenotic vessels or thromboses. One type of procedure is percutaneous transluminal coronary angioplasty, or PTCA, which involves the inflation of an angioplasty balloon catheter in a stenosis to dilate a coronary blood vessel. Additionally, a stent may be implanted in conjunction with this procedure to prevent restenosis, or re-narrowing of the vessel. Various other catheter-based procedures are also common, such as thrombectomy to remove a thrombus or a portion thereof or atherectomy to cut out or abrade a stenosis within a diseased portion of the vessel.
Each of these modalities is associated with a risk that particles will be dislodged during the procedure and migrate through the circulatory system to embolize, possibly causing ischaemia, infarction or stroke. To prevent patient injury from such loosened debris, clinicians may attempt to capture the potentially embolic particles using occlusion devices or embolic filters, then lysing or aspirating the entrapped particles, or removing the particles along with the filter.
Each of these embolic protection devices and methods has certain advantages and certain drawbacks. Occlusion devices will prevent all of the loosened embolic material from migrating. However, since an occluder also prevents blood flow, the duration of use of an occluder is limited. As such, occlusion is not appropriate in all cases. Further, removal of the embolic particles caught by the occluder, such as by aspiration, is an imperfect process, and some embolic particles may escape upon collapsing the occluder.
Embolic filters may be used for longer duration than occluders because filtering devices do not prevent the flow of fluid. Thus, filter devices may be used in a wider variety of procedures, although embolic filters also suffer from some drawbacks. Filters are limited in their ability to remove very small embolic particles from the bloodstream. Additionally, an embolic filter may fill up with debris sufficiently for the filter to occlude the vessel unless the filter is removed or emptied by aspiration.
Medical balloons are sometimes used to deploy implantable filters, such as vena cava filters. This type of filter is typically designed to remain in the body after deployment to serve as a prophylaxis in case a blood clot moves into the major blood vessels. Such filters are detached from the catheter during the procedure. In addition, balloons used for the deployment of this type of filter are not intended to occlude the vessel for capturing embolic particles.
A combination of filters and occluders on the same catheter has been proposed for use in heart surgery where the heart must be arrested and isolated from the rest of the cardiovascular system. One such combination filter and occluder includes a blood filtration assembly for filtering blood and a balloon occluder. However, in such devices, the filter and occluder are generally spatially separated along the shaft of a cannula such that the occluder is positioned upstream of the filter. The separation of the filter and occluder structures is often not practical for use in some procedures, for example an angioplasty procedure.
Another catheter featuring a combination of filter and occluder elements is the subject of co-pending U.S. patent application Ser. No. 10/694,944, commonly assigned to the assignee of the invention herein. In the catheters of the '944 application, a filter surrounds an inflatable occlusion balloon, which requires an elongate lumen to provide fluid communication between the balloon and an inflation/deflation system outside the patient. Such a fluid lumen may undesirably increase the overall diameter of the catheter shaft. Catheters having occlusion balloons must also be carefully designed to avoid fluid leaks, especially from the balloon itself. The '944 application also teaches an embodiment wherein a filter surrounds a non-inflatable occluder that is expandable by push-pull components in addition to those required to operate the filter.
Thus, a need exists in the art for a distal protection catheter having the perfusion benefits of a filter while also offering, selectively, the benefits of complete particle capture found in occluders. A combined embolic filter and non-inflatable occluder may satisfy such a need.